Condensed Statements of Comprehensive Income (Loss) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Net income	$ 195.1	$ 52.7	$ 274.6	$ 60.2
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments, net	(2.0)	9.8	(15.7)	31.7
Unrealized (losses) gains on derivative contracts, net	(3.6)	1.3	(6.1)	(4.4)
Amortization of prior service costs and actuarial losses, net	7.5	4.3	21.0	12.7
Total other comprehensive income (loss), net of tax	1.9	15.4	(0.8)	40.0
Comprehensive income	$ 197.0	$ 68.1	$ 273.8	$ 100.2